A number of 7-amino and 7-acylamino substituted 4, 4a-dihydro-5H-indeno [1, 2-c] pyridazii- 3-0nes have been synthesized as rigid congeners of hypotensive 6-aryl-5-methyl-4, 5- dihydro-3 (2H)-pyridazinones and tested as antihypertensive, antithrombotic, antiulcer, and antiinflammatory agents. Unlike the previously described 7-cyano derivative, which displayed only antiinflammatory action, the new series exhibited significant ...